February 2008doc.: IEEE802.21-08/055r0
IEEE 802.21
Media Independent Handover Services
Message Timestamp
Date:February22, 2008
Authors:Juan Carlos Zuniga, Ulises Olvera-Hernandez
InterDigital Communications LLC
e-Mail:
Abstract
This document presents a solution to the message timestamp that is currently missing in the D9.0 version of the 802.21 specification.
Background
As it was discussed during the 802.21 January 2008 meeting in Taipei, a timestamp indication is missing in some 802.21 messages.
For instance, the Link_Parameters_Report indication primitive and message lack a timestamp associated with the reported parameter. If a packet is delayed before being delivered (either at L2 or L3), the reported parameter could already be expired and the receiver would not be able to tell whether the received delayed message is valid or not
Proposed Solution
The present document proposes a solution to the above mentioned problem by specifying a timestamp field that can be added to the Link_Parameters_Report indication primitive and message.
The proposed timestamp field is based on the short format of the IETF Network Time Protocol v4 [1]. This short format is a 32-bit field (4 octets) that is used in delay and dispersionheader fields where the full resolution and range of the otherformats are not justified. It includes a 16-bit unsigned secondsfield spanning 18+ hours and a 16-bit fraction field resolving 15 microseconds.
Since the 32-bit format does not provide an absolute time with date and time, it can only be used as a reference to a known time or clock. Hence, it is proposed to use the MIH Registration time as reference (i.e. Valid Time Interval start time), as this is a known time registered by both MIH peers.
Update the information to include, update and/or remove the following Information Elements:
On Page 177, Line 40, correct the text as follows
Table B-4—Data types for links
Type Name / Derived From / DefinitionLINK_PARAM_TYPE / CHOICE(
LINK_PARAM_GEN,
LINK_PARAM_QOS,
LINK_PARAM_GG,
LINK_PARAM_EDGE,
LINK_PARAM_ETH,
LINK_PARAM_802_11,
LINK_PARAM_C2K,
LINK_PARAM_FDD,
LINK_PARAM_HRPD,
LINK_PARAM_802_16,
LINK_PARAM_802_20,
LINK_PARAM_802_22,
LINK_PARAM_TIME
) / Measurable link parameter for which
thresholds are being set.
Link parameter types for threshold setting and reporting purposes
On Page 177, Line 27, insert the following:
Type Name / Derived From / DefinitionLINK_PARAM_TIME / CHAR(4) / Timestamp used for measurement reporting.
This is a 32-bit field including a 16-bit unsigned seconds field spanning 18+ hours and a 16-bit fraction field resolving 15 microseconds.
This fields represent the time elapsed since the last MIH Registration time (i.e. Valid Time Interval starting time) at the source or reporting MIH entity, at the time when the report is generated.
In case the last registration was done beyond the timespan of this field, the timestamp field is wraped around.
References
[1] Network Time Protocol Version 4 Protocol and Algorithms Specification, IETF draft-ietf-ntp-ntpv4-proto-08, work in progress
Submissionpage 1Juan Carlos Zuniga, InterDigital